1. Field of the Invention
The present invention relates generally to a method for driving a gas discharge display panel utilized to drive a matrix type of gas discharge display panel, and more particularly to a method for driving a gas discharge display panel in which gas discharge is continued during a maintaining period for a viewer to feel visible light. Also, the present invention relates to a gas discharge display equipment in which the gas discharge display panel is driven according to the method.
2. Description of the Related Art
A color cathode-ray tube (CRT) has been utilized for a color television. Also, a gas discharge display panel has been recently required in place of the CRT to minimize the color television. As is well known, there are two types of gas discharge display panels. One is an alternate current type of gas discharge display panel, and another is a direct current type of gas discharge display panel. The direct current type of gas discharge display panel is superior for practical use as compared with the alternate current type of gas discharge display panel.
2.1. Previously Proposed Art
A conventional method for driving a gas discharge display panel according to a pulse memory process is described. The conventional method has been proposed by Murakami in a paper J73-C-11 published by Institute of Telecommunications Engineers.
FIG. 1 is a plan view of a gas discharge display panel driven according to a pulse memory process.
As shown in FIG. 1, a gas discharge display panel 151 is provided with a group of scanning electrodes 152 formed of a plurality of cathode lines C1 to Cm arranged in parallel, a group of display electrodes 153 formed of a plurality of anode lines A1 to An which are arranged in parallel and cross over the scanning electrodes 152, and a plurality of display cells 154 arranged at intersection spaces between the cathode lines and the anode lines. Each of the display cells 154 is filled with discharge gas such as helium-xenon gas, and fluorescent material is applied on a surface of each of the display cells 154. Therefore, when a comparatively high electric potential difference is generated between the cathode line and the anode line, gas discharge is produced in the discharge gas so that ultraviolet light is radiated from the discharge gas. The ultraviolet light is changed to visible light by the action of the fluorescent material so that a viewer can feel the visible light.
In the above configuration, as shown in FIG. 2, a series of maintaining pulses Pm having a positive voltage V.sub.A is always applied on each of the anode lines A1 to An, and a scanning pulse Ps having a negative voltage Vsc is applied on each of the cathode lines C1 to Cm according to pieces of display information.
When a piece of display information is, for example, transferred to a display control section (not shown) to produce visible light in a specific display cell 154a arranged at the intersection space between the cathode line C2 and the anode line A2, a scanning pulse Ps is applied on the cathode line C2 in non-synchronism with the maintaining pulses Pm, and a writing pulse Pw having a positive voltage Vw is applied on the anode line A2 in synchronism with the scanning pulse Ps. Therefore, writing gas discharge is produced in the discharge gas filled in the specific display cell 154a. In this case, a gas discharge starting electric potential difference required to initially produce gas discharge in the display cells 154 is comparatively high. Therefore, the writing gas discharge is produced while applying the scanning pulse Pw. After the writing gas discharge is produced, excited particles are temporarily generated in the specific gas cell. Therefore, gas discharge subsequent to the writing gas discharge is easily produced at a comparatively low electric potential difference.
Thereafter, a series of maintaining pulses Pm is applied on the anode line A2 to intermittently produce maintaining gas discharge during a maintaining period in the specific display cell 154a. In this case, a maintaining negative voltage Vca higher than the negative voltage Vsc of the scanning pulse Ps is continuously applied on the cathode line C2. Therefore, a viewer can feel visible light.
After the maintaining period passes, an erasing pulse Per having an erasing negative voltage V.sub.E is applied on the cathode line C2 to stop the maintaining gas discharge. The erasing voltage V.sub.E of the erasing pulse Per is higher than the maintaining voltage Vca. Therefore, the maintaining gas discharge is stopped. Thereafter, even though the maintaining pulses Pm is applied on the anode line A2 and the maintaining voltage Vca is continuously applied on the cathode line C2, any gas discharge is not produced in the specific display cell 154a because the gas discharge starting electric potential difference is comparatively high.
Accordingly, because the maintaining gas discharge is intermittently produced during the maintaining period, the brightness of the visible light can be sufficiently high. For example, the maximum brightness of the visible light reaches a practical level 100 candela/m.sup.2.
2.2. Another Previously Proposed Art
FIG. 3 is a plan view of a matrix type of gas discharge display panel having an electrode structure conventionally utilized. A matrix type of gas discharge display panel 200 shown in FIG. 3 has been conventionally developed as one of gas discharge display panels. The display panel 200 was laid open to public inspection under Provisional Publication No. S57-86886 (Japanese Patent Application No. S55-162709).
FIG. 4 shows waveforms of various signals transmitted in the display panel shown in FIG. 3.
As shown in FIG. 3, the gas discharge display panel 200 is provided with a plurality of cathode lines 201 arranged in a row direction at first and second regular intervals, a plurality of display anode lines 203 arranged in a line direction while crossing over the cathode lines 201 at third regular intervals, a plurality of display cells 202 arranged at intersection spaces between the cathode lines 201 and the display anode lines 203, a plurality of subsidiary anode lines 205 arranged in parallel to the display anode lines 203 and between the display anode lines 203, and a plurality of subsidiary cells 204 arranged at intersection spaces between the cathode lines 201 and the subsidiary anode lines 205.
Each of the subsidiary anode lines 205 is positioned every two display anode lines 203 so that each of the display cells 202 faces only one of the subsidiary cells 204.
Each of the subsidiary anode lines 205 is always applied at a subsidiary anode voltage Vsa through a resistor (not shown) having a high resistance. Each of the cathode lines 201 is normally applied at a maintaining cathode voltage Vca. Maintaining anode pulse signals Sap are always transmitted on each of the display anode lines 203 at a regular cycle T. Each of the maintaining anode pulse signals Sap has a pulse width .tau.ap and a peak voltage Vap.
In the above configuration, a scanning pulse signal Scp is applied to each of the cathode lines 201. The scanning pulse signal Scp has a pulse width .tau.cp and a peak voltage Vcp. As shown in FIG. 4, when a first scanning pulse signal Scp is initially transmitted on a first line C1 of the cathode lines 201, a subsidiary cell current Is.sub.1 flows from the subsidiary anode lines 205 to the first line C1 through first subsidiary cells 204 arranged at the intersection spaces between the first line C1 and the subsidiary anode lines 205. Therefore, subsidiary gas discharge is produced in the first subsidiary cells 204. In contrast, because all of the display anode lines 203 are maintained at a zero voltage, a first display cell current Id.sub.1 does not flow through any of the display cells 202. Therefore, writing gas discharge is not produced in any of the display cells 202.
When a second scanning pulse signal Scp is thereafter transmitted on a second line C2 of the cathode lines 201, a writing pulse signal Sw is applied on a second line DA2 of the display anode lines 203 in synchronism with the second scanning pulse signal Scp. The writing pulse signal Sw has a pulse width .tau.w and a peak voltage Vw. Therefore, a subsidiary cell current Is.sub.2 flows from the subsidiary anode lines 205 to the second line C2 through second subsidiary cells 204 arranged at the intersection spaces between the second line C2 and the subsidiary anode lines 205. Therefore, subsidiary gas discharge is produced in the second subsidiary cells 204. Also, because the writing pulse signal Sw is applied on the second line DA2 in synchronism with the second scanning pulse signal Scp, a second display cell current Id.sub.2 flows through a specific display cell 202 arranged at the intersection space between the second line C2 and the second line DA2. Therefore, writing gas discharge is produced in the specific display cell 202, and visible light is radiated from the specific display cell 202 to a viewer.
In this case, because excited particles are produced in both the specific display cell 202 and the second subsidiary cell 204 facing the specific display cell 202, the specific display cell 202 and the second subsidiary cell 204 facing the specific display cell 202 are coupled to each other through the excited particles which function as priming. As a result, the writing gas discharge is produced in the specific display cell 202 at sufficiently high speed.
Thereafter, because the maintaining anode pulse signal Sap is always transmitted on the second line C2 of the display anode lines 203, subsequent display cell currents Ids subsequent to the second display cell current Id.sub.2 intermittently flow through the specific display cell 202 in synchronism with pulses of the maintaining anode pulse signal Sap. In this case, maintaining gas discharge is intermittently produced in the specific display cell 202 during a maintaining period. Accordingly the viewer can continuously feel the visible light during the maintaining period. After the maintaining period passes, an erasing period subsequent to the maintaining period is started. Therefore, an erasing signal Ser having a voltage Ver is transmitted on the second line C2 of the cathode lines 201 to stop the maintaining gas discharge produced in the specific display cell 202. Therefore, the visible light radiated from the specific display cell 202 is stopped by the erasing signal Ser.
When a third scanning pulse signal Scp is thereafter transmitted on a third line C3 of the cathode lines 201, a subsidiary cell current Is.sub.3 flows from the subsidiary anode lines 205 to the third line C3 through third subsidiary cells 204 arranged at the intersection spaces between the third line C3 and the subsidiary anode lines 205. Therefore, subsidiary gas discharge is produced in the third subsidiary cells 204. In contrast, because all of the display anode lines 203 are maintained at a zero voltage, writing gas discharge is not produced in the display cells 202 in the same manner as in the first scanning pulse signal Scp. Therefore, even though the maintaining anode pulse signals Sap are transmitted on the display anode lines 203 after the third scanning pulse signal Scp is transmitted on the third line C3, a third display cell current Id.sub.3 does not flow through any of the display cells 202.
Accordingly, in cases where a writing pulse signal Sw is applied on a display anode line 203 in synchronism with a scanning pulse signal Scp, visible light can be radiated from the display cell 202.
Also, because excited particles are produced between the display cell 202 and a subsidiary cell 204 facing the specific display cell 202, the visible light can be radiated at sufficiently high speed.
2.3. Problems to be solved by the Invention
However, there are many drawbacks in the conventional method for driving the gas discharge display panel 151
That is, two circuits are additionally required to drive the gas discharge display panel 151 according to the conventional method. One of the circuits is required to generate the maintaining pulses Pm and the writing pulses Pw. The other circuit is required to generate the scanning pulses Ps and the erasing pulses Per. As a result, the circuits are complicated. Also, because the maintaining pulses Pm are always applied on the anode lines, an electric power required to generate the maintaining pulses Pm is consumed in vain during a non-display period subsequent to the maintaining period without radiating the visible light.
Also, there are many drawbacks in the conventional method for driving the gas discharge display panel 200.
That is, the maintaining anode pulse signals Sap are always transmitted on each of the display anode lines 203 regardless of whether the maintaining gas discharge is produced in the specific display cell 202. Therefore, after the maintaining gas discharge is stopped, an electric power required to continuously generate the maintaining anode pulse signals Sap is unavailingly consumed as an electric power loss because the electric power is not contributed to the maintaining gas discharge in the gas discharge display panel 200.
In detail, because the maintaining anode pulse signals Sap are always applied on the display anode lines 203 without producing the maintaining gas discharge, an electric power loss P is substantially expressed by an equation (1). EQU P=(m*n*C.sub.o *Vap.sup.2)/T (2)
where the symbol m denotes the number of cathode lines 201, the symbol n denotes the number of display anode lines 203, the symbol C.sub.o denotes a capacitance of one of the display cells 202 arranged between the cathode lines 201 and the display anode lines 203, the symbol Vap denotes a peak voltage of the maintaining anode pulse signals Sap, and the symbol T is a cycle of the maintaining anode pulse signals Sap.
As is formulated in the equation (1), in cases where the gas discharge display panel 200 is manufactured in large-sized one, the electric power loss P is increased in proportion as the number of cathode lines 201 and/or the number of display anode lines 203 are increased. Also, the electric power loss P is increased in proportion as the cycle T of the maintaining anode pulse signals Sap is shortened. As a result, a driving efficiency in the gas discharge display panel 200 deteriorates.
Also, because the writing pulse signal Sw and the maintaining anode pulse signals Sap are transmitted on the display anode lines 203, the preparation of three types of voltages such as 0, Vw, and Vap are required. Also, because the maintaining cathode voltage Vca, the scanning pulse signal Scp, and the erasing pulse signal Ser are transmitted on the cathode lines 201, the preparation of three types of voltages such as Vca, Vcp, and Ver are required. As a result, a driving circuit in which those signals are produced is complicated and becomes large.